A wide range of arrowhead designs suitable for archery are commercially available. One category of arrowheads is the broadhead—a bladed arrowhead featuring multiple sharp cutting blades that are designed to greatly increase the effective cutting area of the arrowhead when it impacts a target. Broadheads are popular in the bowhunting industry, as the increased cutting radius of a broadhead results in larger entrance and exit wounds in a game animal struck by the broadhead, causing increased blood loss which kills the animal quickly and humanely, and provides a better blood trail for tracking and retrieval of the carcass.
While broadheads provide an improved cutting capability when compared to non-bladed field point or nib point arrowheads, some broadhead designs suffer from inferior aerodynamic properties in comparison with their non-bladed counterparts. The blades of the broadhead, if deployed during the flight of an arrow, can result in undesirable effects and cause the arrow to veer off course from the flight path.
Prior art broadhead designs have attempted to resolve the aerodynamic issues by retaining, at least in part, the deployable cutting blades of the broadhead within the ferrule body of the broadhead during flight. Upon impacting the target, the blades are deployed, moving outwardly from the ferrule body and exposing the sharp cutting edges of the blades once fully deployed. Such designs are known by those skilled in the art as an “expandable broadhead.” Some prior art expandable broadheads are disclosed in U.S. Pat. Nos. 8,197,367 and 8,986,141, which are hereby incorporated by reference.
FIG. 1 illustrates one such prior art expandable broadhead 100 having two deployable blades 105a and 105b. A retaining device 120 is provided for retaining the deployable blades 105a and 105b in a retracted configuration within a ferrule body 110. The expandable broadhead 100 includes a two-sided “cut-on-contact” tip 115, which is a sharpened double-edged piece of steel inserted within the ferrule body 110, and is designed to penetrate the hide of a target game animal while requiring a relatively small amount of energy for penetration.
Some expandable broadheads 100 are composed of metals such as stainless steel or aluminum alloys. However, manufacturing a broadhead out of titanium would offer several benefits. The weight of an expandable broadhead is at a premium, and lower weight materials enable broadhead designers to provide additional strength and cutting ability to the broadhead. Titanium has a high strength to weight ratio. While titanium's strength is similar to that of steel, it's density is approximately 60% less than the density of steel that is typically used in broadheads. For example, the density of titanium is approximately 0.160 pounds per cubic inch, while steel has a density of about 0.284 pounds per cubic inch. And, Grade 5 titanium has a yield strength of approximately 140,000 pounds per square inch when solution treated and aged, compared to the approximately 130,000 to 160,000 pounds per square inch yield strength of steel alloys commonly used in broadheads.
The relatively low weight and high strength of titanium makes it an attractive option for use in broadheads. However, known techniques for manufacturing titanium broadheads have disadvantages. For example, known processes manufacture titanium broadheads from titanium bar stock, which is expensive relative to the cost of steel and aluminum. And, titanium's high strength, abrasiveness, and low heat transfer coefficient cause the machining tools to overheat and wear out quickly. As such, manufacturing broadheads from the titanium bar stock are expensive and time consuming.
Moreover, in some designs, using titanium bar stock results in up to 90% waste, further increasing manufacturing costs. For example, approximately 0.033884 pounds (237 grains) of titanium bar stock would be required to machine one broadhead 100 of approximately 0.008424 pounds (59 grains). This results in a material scrap or waste of over 75%.